Which of the following is the MOST secure method of storing critical and sensitive system information (e.g. administrative passwords, trusted signing keys)?

Storing encrypted data offline in a physical safe provides two independent layers of protection - encryption guards against digital compromise and the physical safe guards against unauthorized physical access. The offline nature eliminates any network-based attack surface, making this an air-gapped solution that satisfies both confidentiality and availability requirements for critical secrets.

ZIP file password encryption uses weak algorithms (ZipCrypto or AES-256 depending on implementation) and the file remains accessible to anyone who obtains it, with no physical access control.

Full disk encryption protects data at rest on a connected drive, but the drive may still be accessible over a network or if the system is compromised while running.

An encrypted virtual disk is still hosted on a live system and accessible when mounted, exposing it to memory attacks, privilege escalation, and network-based threats.